I'm not surprised you're feeling like this.
Let's break it down into manageable chunks. Have you been to see a solicitor yet about the financial arrangements?
Have you told work what's been going on, so they can cut you a bit of slack at the moment?
Is there any workplace counselling available, or financial advice?
With friends, how would you feel about choosing the one you feel closest to and ringing her and saying you need some support at the moment? Most friends will feel flattered at being asked and will be only too happy to help, but a good tip is to ask that friend how much time she can give you right now. Urge her to be honest and take no offence if it's not as much as you're going to need. Most of us have some capacity in our lives though, to help a friend in need.
Next, the holiday. Once you know what the finances are going to be, work out what you can afford. I'm sure that by the summer, you're going to need a holiday and it can be a liberating experience too, knowing that you can do this on your own. Don't under-estimate how looking forward to and planning a holiday might be a great distraction at the moment for you and the DCs and it doesn't have to cost a fortune. I think you'll get more fun out of having a holiday than just the holiday itself, too.
Start writing a journal about how you're feeling. This will help you to process your thoughts and in time, see how far you've come.
Having read your other threads, start to project how much better off you're going to be, now this man has gone. Recall what you were sacrificing for this relationship and what a drain he was. You're free of that now and he's someone else's problem.